REPORT DOCUMENTATION FORM WATER RESOURCES …WATER RESOURCES RESEARCH CEmER UniversityofHawaii atManoa 1 SERIfS NUMBER Technical ReportNo. 179 2 COWRR FlELD-GROUP 02-F;07-C 3 1TILE

REPORT DOCUMENTATION FORMWATER RESOURCES RESEARCH CEmER

University of Hawaii at Manoa1 SERIfS

NUMBER Technical Report No. 1792

COWRRFlELD-GROUP 02-F; 07-C

3 1TILE

Aquifer identification and classification for Oahu:Groundwater protection strategy for Hawaii

8AUIHORS

"REPORTDATE

5NO. OFPAGES

6NO. OFTABLES

9GRAm AGENCY

February 1990 (Rev.)

vii + 28

17NO.OF

1 FIGURES 15

John F. Mink Department of Health, State of HawaiiL. Stephen Lau

10coNTRAcrNUMBER T-763

11DESCRIPTORS: *aquifers, *aquifer characteristics, *aquifer systems, groundwater

IDENTIFIERS: *aquifer classification, *Aquifer Code, *groundwater protection strategy,*Class I groundwaters, Oahu, Hawaii

12ABSTRAcr (PURPOSE, METIIOD, RESULTS, CONCLUSIONS)

In response to the need to identify and describe aquifers for each island of the state of Hawaii to serveas a frameworlc for groundwater protection strategy, a program has been initiated to classify and assigncodes to the principal aquifers ofthe State. This firSt report provides Aquifer Codes and Status Codesfor the island of Oahu. The Aquifer Codes incorporate locational and descriptive indices, while theStatus Codes indicate the developability, utility, quality, uniqueness and vulnerability to contaminationof the groundwater resources. The codes were generated for Hawaiian conditions of groundwateroccurrence and behavior in preference to employing the DRASTIC approach suggested by the U.S.EPA. Each Aquifer Type within an Aquifer System is assigned an Aquifer Code consisting of an eightdigit number. An Aquifer Code is unique and non-repeatable in the State. Accompanying the AquiferCode is a Status Code of five digits. A Status Code is specific to an Aquifer Code. The Oahuclassification includes 6 Aquifer Sectors, 24 Aquifer Systems, and 90 Aquifer Codes.

Street· Honolulu, Hawaii 96822· U.S.A. • (808) 948-7847

AUTHORS:

Mr. John F. MinkConsultantWater Resources-Earth SciencesP.O. Box 4452Honolulu, Hawaii 96813Tel.: 808n37-6136

and

Research AffiliateWater Resources Research CenterUniversity of Hawaii at ManoaHonolulu, Hawaii 96822

Dr. L. Stephen LauDirectorWater Resources Research CenterUniversity of Hawaii at Manoa2540 Dole StreetHonolulu, Hawaii 96822Tel.: 808/956-7847FAX: 808/956-5044

AQUIFER IDENTIFICATION AND CLASSIFICATION FOR O'AHU:Groundwater Protection Strategy for Hawai'i

John F. Mink

L. Stephen Lau

Technical Report No. 179

November 1987(Rev. 1990)

Project Completion Report

for

Identification of Class I: Special GroundwatersHighly Vulnerable to Contamination, Oahu

Project No.: T-763

Principal Investigator: L. Stephen Lau

Project Period: 1 June 1986-30 November 1987

Funding Agency: Department of Health, State of Hawaii

WATER RESOURCES RESEARCH CENTERUNIVERSITY OF HAWAll AT MANOA

Honolulu, Hawaii 96822

v

ABSTRACT

In response to the need to identify and describe aquifers for each island of the state of Hawai'i

to serve as a framework for groundwater protection strategy, a program has been initiated to

classify and assign codes to the principal aquifers of the State. This fIrst report provides

Aquifer Codes and Status Codes for the island of O'ahu.

The Aquifer Codes incorporate locational and descriptive indices, while the Status Codes

indicate the developability, utility, quality, uniqueness and vulnerability to contamination of the

groundwater resources.· The codes were generated for Hawaiian conditions of groundwater

occurrence and behavior in preference to employing the DRASTIC approach suggested by the

U.S. EPA.

Each Aquifer Type within an Aquifer System is assigned an Aquifer Code consisting of an

eight-digit number. An Aquifer Code is unique and non-repeatable in the State. Accompanying

the Aquifer Code is a Status Code of fIve digits. A Status Code is specifIc to an Aquifer Code.

The O'ahu classification includes 6 Aquifer Sectors, 24 Aquifer Systems, and 90 Aquifer

Codes.

vii

CONTENTS

ABSIRACT............................................................... v

GROUNDWATERCONTAMINATIONVULNERABILITY 1

INAPPLICABILITY OF DRASTIC RATING SYSTEMOF POLLUTION POTENTIAL IN HAWAI'I. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

AQUIFER CLASSIFICATION AND AQUIFER CODES. . . . . . . . . . . . . . . . . . . . . . . . . .. . . 6

GROUNDWATER PROTECTION: STATUS CODE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

AQUIFER CLASSIFICATION MAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

REFERENCES 11

LAYOUT OF AQUIFER SECTORS AND SYSTEMS FOR O'AHU . . . . . . . . . . . . . . . . . . . . . 12

AQUIFER CLASSIFICATION EXPLANATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figures

1.1. Aquifer Classification Map, Ka'ena, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.2. Aquifer Classification Map, Wai'anae, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.3. Aquifer Classification Map, Waimea, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.4. Aquifer Classification Map, Hale'iwa, O'ahu, Hawai'i .... . . . . . . . . . . . . . . . . . . . . . 17

1.5. Aquifer Classification Map, Schofield Barracks, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . 18

1.6. Aquifer Classification Map, 'Ewa, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.7. Aquifer Classification Map, Kahuku, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.8. Aquifer Classification Map, Hau'ula, O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . 21

1.9. Aquifer Classification Map, Waipahu, O'ahu, Hawai'i. . . . . . . . . . . . . . . . . . . . . . . . . . 22

1.10. Aquifer Classification Map, Pearl Harbor, O'ahu, Hawai'i 23

1.11. Aquifer Classification Map, Kahana, O'ahu, Hawai'i 24

1.12. Aquifer Classification Map, Kane'ohe, Oahu, Hawai'i. . . . . . . . . . . . . . . . . . . . . . . . . . 25

1.13. Aquifer ClassificationMap, Honolulu, O'ahii,-Hawai'i : . . . . . . . . . 26

1.14. Aquifer Classification Map, Mokapu, Oahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1.15. Aquifer Classification Map, Koko Head, O'ahu, Hawai'i 28

Table

1. Aquifer and Status Codes for O'ahu, Hawai'i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

GROUNDWATER CONTAMINATION VULNERABILITY

Until a few years ago, Hawai'i groundwater contamination problems were few in number and

investigations comparatively minor in scale (Lau and Mink 1987). The quality of much of

Hawai'i groundwater is outstanding; thus, water can be consumed safely without prior treat

ment. For this and other reasons, groundwater has been the prime source for municipal and

general domestic supply throughout Hawai'i, especially on O'ahu, the most populous island in

the State. It is not surprising, then, that the discovery of volatile organic chemicals in a number

of wells in the Pearl Harbor Aquifer, one of the principal sources of potable groundwater in

O'ahu, was a shock to the public as well as to the scientific and engineering community. The

Hawaii State Department of Health responded to this discovery by initiating a groundwater

protection strategy consistent with the goals of the U.S. Environmental Protection Agency.

Aquifer identification and assignment of contamination vulnerability indices to groundwater are

important phases of the protection program.

A fundamental objective of groundwater protection strategy is to classify aquifers according

to hydrogeologic parameters, and groundwater by quality characteristics relative to beneficial

uses. Natural groundwater quality is the result of hydrogeochemical processes; however, this

pristine quality can be degraded by anthropogenic activities. Thus, the protection of ground

water resources must contend with land use practices. Aquifer identification and location are

therefore fundamental to formulation of the protection strategy.

The quality of native groundwater is the result of the environments through which infil

tration water passes and in which water moves and accumulates. Among the obvious con

tributors to the chemistry of groundwater in an aquifer are the quality of the original water that

recharges into the ground, the chemical properties of soils and rocks through which the water

passes, residence time of the water in the saturated zone, and quality of waters with which the

new water mixes. Seawater intrusion also adds salts to all basal groundwater in Hawai'i.

Activities, such as irrigated agriculture and wastewater injection, may significantly alter

groundwater quality. Moderate increases in concentrations of nitrate, chloride, sulfate, and

silica are attributable to prolonged irrigation of sugarcane. Introduction of organic chemicals-Irom--pestiaaes,-herblClde-s~- an(rnematicTdes--acco~pany ~odern-~~ic~itur~~- Vn1~~ily ~~ --- ---

large-scale use of the land can result in some degree of contamination.

Hawai'i has effectively used land management as a strategy to protect groundwater quality.

A good example is the establishment of the Conservation District around the high rainfall zone

of the Ko'olau Range on O'ahu. This region is retained in as natural a state as possible to

enhance groundwater recharge and to protect the purity of the rainfall that' percolates into the

2

subsurface. Another example is the State regulation that controls underground injection. A "no

pass" line sets off regions in which direct injection of wastewater is prohibited.

Between these two lines-the Conservation District and the injection line-falls most of

each island's land area. The unregulated areas are largely underlaid by unconfmed aquifers that

are potentially vulnerable to contamination. Urbanization and agriculture dominate land use.

Manifestly, a strategy must be devised to prevent contamination by activities that range from

dry cleaning to chemically based agriculture.

The aquifer classification scheme and contamination indices provided in this study are con

sistent with the U.S. EPA (1984) Groundwater Protection Guidelines. They are also consistent

with and complementary to Hawaii State water quality regulations for protecting surface water.

In Hawai'i, surface water is classified by ecosystem and associated water quality. In the

strategy for groundwater, the resources are classified by hydrogeology and water quality.

INAPPLICABILITY OF DRASTIC RATING SYSTEMOF POLLUTION POTENTIAL IN HAWAIII

Except in aquifers covered and confined by caprock, virtually all groundwater in O'ahu is

accessible to contamination accompanying infiltration. In the Status Codes listed in Table 1,

most Aquifer Types are rated as highly vulnerable to contamination.

Evaluating contamination vulnerability by using the DRASTIC approach suggested by EPA is

not very useful for the aquifers of O'ahu, or the other islands of the state. DRASTIC is an

acronym for a list of physical characteristics that describe a hydrogeological setting. These

characteristics are D, depth to water; R, recharge; A, aquifer media; S, soil media; T, topogra

phy; I, infiltration in the vadose zone; and C, aquifer conductivity. Two sets of relative weights

are assigned to each characteristic: one for areas where agriculture is the dominant land use; the

other for mixed usage. The relative weights are as follows:

Agriculture OtherD 5 5R 4 41\ --3- -S 5 2T 3 1145C 2 3

Weighting choices are inevitably subject to considerable arbitrariness.

To compute the pollution potential, each DRASTIC factor is divided into a range scale of 1 to

10, in which 1 assigns the least importance to the factor and 10 the most. Thus, the

4TABLE l.--Continued

Is.Aquifer Aquifer Aquifer Aquifer Status QuadrangleSector System Type Code Code No.

3 03 Waianae 02 Lualualei 116 30302116 13311 2,5122 30302122 23323112 30302112 23321 2, 5

212 30302212 11111 2, 5

03 Waianae 116 30303116 13311 2122 30303122 23223

112 30303112 11111 2

232 30303232 11111 1,2,4,5

04 Makaha 116 30304116 13321 2122 30304122 11113112 30304112 11111 2

232 30304232 11111 1,2,4

05 Keaau 116 30305116 33421 1122 30305122 11212112 30305112 21211 1,2

212 30305212 21111 1,2

04 North 01 Mokuleia 116 30401116 13221 1,4121 30401121 11113111 30401111 11111 1,4

212 30401212 21111 1,4,5

02 Waialua 116 30402116 12211 4121 30402121 11213111 30402111 11111 4,8

03 Kawailoa 116 30403116 12211 3,4121 30403121 12313111 30403111 11111 3,4,7,8

112 30403112 11111 3,7116 30403116 12211 3, 7112 30403112 21112212 30403212 21111 3,7,8

05 Central 01 Wahiawa 212 30501212 11111 4,5,8,9

02 Koolau 212 30502212 11111 8---~--- -

06 Wmdward 01 Koolauloa 116 3060III6 12211 7,8,11121 30601121 12213111 30601111 11111 7,8,11

212 30601212 21111 7,8,11

112 30601112 11111 7116 30601116 22221 7122 30601122 21122

02 Kahana 116 30602116 12211 11122 30602122 11113112 30602112 11111 11

3 06 Windward

TABLE l.-Continued

Is. AquiferSector

AquiferSystem

02 Kahana

03 Koolaupoko

04 Waimanalo

5

Aquifer Aquifer Status QuadrangleType Code Code No.

212 30602212 11111 8,11

116 30603116 12211 12122 30603122 11122212 30603212 11111 11, 12, 13

116 30604116 12211 14, 15122 30604122 11113212 30604212 11111 12, 13, 14, 15

NOTE: Rev. 1990

fonnula becomes

D(w)D(r) + R(w)R(r) + ... + C(w)C(r) =potential pollution

in which w refers to the weight and r to the range.

The above may have utility where the surface-subsurface pathways of infiltration take place

in a wide variety of natural environments, but in Hawai'i the range is limited and the pathways

direct. Each of the DRASTIC factors is relatively simple to describe for Hawai'i conditions on a

regional scale and may be capsulized as follows.

D (depth to water). The water table in all unconfined basal aquifers is 40 ft (12.19 m) or

less above sea level. In confined basal aquifers the water surface is at the base of the caprock.

Depth to water in high level aquifers is variable. For all unconfined aquifers, depth to water

does not significantly influence the removal of refractory contaminants, such as many volatile

organic compounds. Microbiological pollutants, on the other hand, are commonly attenuated in

the relatively thin surface soil.

R (recharge). Natural infiltration is directly related to rainfall, and the highest rainfall

occurs at elevations between 1500 and 5000 ft (457.2 and 1 524 m). However, direct recharge

to unconfined aquifers takes place everywhere, even in the driest parts of the islands. Nowhere

in Hawai'i, ~o matter how low the average annual rainfall, suffers a complete absence of

recharge.

A (aquifer media). Virtually every important potable groundwater aquifer in the Hawaiian

Islands is composed of basalts that were extruded dUring the primary mountain bUilding phase ------- ---

of volcanism. These basalts have similar aquifer properties. The only other regional aquifers

are in limestones carrying nonpotable to brackish water. Aquifers in sediments and post

erosional volcanics are small.

S(soil media). Soils fonned in place on basalts are strikingly similar in being highly per

meable and readily infiltrable. These are the most common soils above an elevation of about

100 ft (30.5 m). At lower elevations the hydromorphic soils are less penneable.

6

T (topography). Land configuration in Hawai'i is generally irrelevant as a direct influence

on the recharge of groundwater. In steep topography the runoff-rainfall ratio is high, but even

here significant infiltration takes place.

I (infiltration in vadose zone). In unsaturated rock beneath the soil-saprolite cover, infil

tration follows a fairly direct path to the unsaturated zone.

C (conductivity of aquifer). All of the main Hawai'i aquifers in basalt are extremely per

meable with hydraulic conductivities in excess of 1000 ft (304.8 m)/day on a regional scale.

Limestone aquifers are also highly permeable, while sediments are generally poorly permeable.

The alkalic series of volcanic rocks that followed the primary basalts are moderately permeable.

The DRASTIC method of estimating pollution potential in Hawai'i has limited applicability,

but in a modified form it can be useful in organizing an environmental data base for examining

contamination problems.

AQUIFER CLASSIFICATION AND AQUIFER CODES

Shortly before the Hawaii State Department of Health initiated the groundwater protection pro

gram, work had begun in classifying and systematizing groundwater occurrences by the

University of Hawaii Water Resources Research Center (Mink and Sumida 1984). This work

was a follow-up to an earlier classification attempt sponsored by the Department of Health as

part of the original Underground Injection Control program (First West Engineers 1978).

The classification scheme reported by Mink and Sumida (1984) is the starting point for

developing an Aquifer Code. Classification is based on a hierarchy of descriptors beginning

with general location by Island and Aquifer Sector, to which b~longs a set of Aquifer Systems,

within which are a variety of Aquifer Types. Sectors primarily reflect broad hydrogeological

features and, secondarily, geography. Aquifer Systems are more specifically defined by

hydrogeologic continuity, in particular hydraulic connections among units; Aquifer Types are

differentiated by distinctive features of hydrology and geology.

In brief, the hierarchy is as follows:

a. Island-The global locator

b. Sector-A large region with hydrogeological similarities

c. System--An area within a Sector showing hydrogeological continuity

d. Type-Portions of a System having the same hydrological and geological features.

Islands are coded by number in conformance with the U.S. Geological Survey (1975)

protocol. Each Sector is coded with a two-digit number and by a geographic name except

where locational confusion might result, in which case the general locators North, South, East,

7

and West, or a traditional geographic tenn such as Windward, are used. A two-digit number is

applied to each Aquifer System, which also can be referred to by a geographic name. Three

digits describe fundamental hydrology and geology to constitute the Aquifer Type.

The numerical code has the fonn, 1 11 11 111, in which the fIrst number is the Island, the

next two represent the Sector, the following two the System, and the last three the Type. Island

numbers are 1 (Ni'ihau), 2 (Kaua'i), 3 (O'ahu), 4 (Moloka'i), 5 (Uina'i), 6 (Maui),

7 (Kaho'olawe), and 8 (Hawai'i). Sector numbers start at 01 in each Island, and System

numbers also start at 01 in each Sector.

Hydrology is uniquely described by a pair of digits and geology by a single digit. Identi

fying characteristics with their codes are as follows.

HYDROLOOY. Aquifer Types are defined as either basal or high level, and as either uncon

fined or confmed. Their numbers with brief descriptions are as follows:

No. Type

1 Basal

2 High Level

1 Unconfined

2 Confined

3 Confined orUnconfined

Description

Fresh water in contact with seawater

Fresh water not in contact with seawater

Where the water table is the upper surface ofthe saturated aquifer

Aquifer is bounded by impenneable or poorlypermeable fonnations; top of the saturatedaquifer is below the surface of thegroundwater

Where the actual condition is uncertain.

Using the above coding, groundwater can be 11 or 12, or 21 or 22. Where confIning

conditions are unclear, the second digit is taken as 3.

GEOLOOY. Aquifers are categorized as occurring in the flank lavas of the volcanic domes,

in rift zones characterized by dikes, on poorly penneable perching members, or within the

sedimentary sequence. Flank aquifers nonnally are horizontally extensive and display the low

est heads and usually carry basal water; rift aquifers are segmented into compartments by dikes;

rched-aquifers-lie-o-n impenneaolefonnationsout are not orainanly very extensive; and

sedimentary aquifers are comprised of alluvial and marine sediments deposited by erosion and

biogenic processes. The geologic codes are as follows:

No. Type Description

1 Flank Horizontally extensive lavas

2 Dike Aquifers in dike compartments

3 Flank/Dike Indistinguishable

8

4 Perched Aquifer on an impermeable layer

5 Dike/Perched Indistinguishable

6 Sedimentary Non-volcanic lithology

One of the above numbers attached to the two hydrology numbers defmes the Aquifer

Type.

The sequence of all numbers from Island through geology is called the Aquifer Code. Each

Aquifer Type has an eight-digit code which is unique. An example of an Aquifer Code for

groundwater occurrence in O'ahu is

3 O'ahu Island

01 Honolulu Sector

04 Moanalua Aquifer System

111 Basal Unconfmed Flank

The Aquifer Code for the above is 30104111. There can be no repetition elsewhere in the State.

The code is suited to computer data basing having great retrieval flexibility.

A variety of important information related to the aquifers can be appended to each Aquifer

Code. Certain hydrogeological parameters and quantities, such as rainfall, infiltration, sus

tainable yield and storage, can be appended to the code to expand its utility. For example, items

relevant to groundwater contamination can be expressed as a separate numerical code and

attached to the Aquifer Code.

Table 1 lists the Aquifer Codes for the island of O'ahu along with Sector and Aquifer

System names. O'ahu includes 6 Sectors, 24 Aquifer Systems, and 90 Aquifer Codes. Also

listed is the Status Code of each Aquifer Type. The Status Code, which is described in the next

section, summarizes elements crucial to the groundwater protection strategy.

GROUNDWATER PROTECTION: STATUS CODE

Concepts of EPA's groundwater classification conforming to Hawai'i conditions are used to

.::cd=ev-'-'l=·s-=-e a ~oundwater Status Code that describes development ~tage, utility, salinity, unique

ness, and vulnerability to contamination of the aquifers. The Status Code is conveniently

attached to the Aquifer Code, and the combination is an efficient representation of location,

hydrology, geology, utility, water quality, and contamination potential of groundwater

resources in every part of the island.

The five-digit Status Code consists of a single number from each of five separate descrip

tive categories. The categories and their status elements with identifying numbers are as

follows:

9

A. Development Stage

1. Currently used

2. Potential use

3. No potential use

B. Utility

1. Drinking

2. Ecologically important

3. Neither

C. Salinity (mgll cn1. Fresh «250)

2. Low (250 -1000)

3. ~oderate(I000-5000)

4. High (5000-15,000)

5. Seawater (>15,(00)

D. Uniqueness

1. Irreplaceable

2. Replaceable

E. Vulnerability to Contamination

1. High

2. ~oderate

3. Low

4. None

Only one number from each major category listed above is allowable in the Status Code.

For instance, a currently developed groundwater source (1), used for drinking (1), having a

salinity ofless than 250 mg/l Cl- (1), being irreplaceable (1) and highly vulnerable to contami

nation (1), would have the Status Code 11111. If it were ecologically important but not suitable

for drinking with a salinity of 750 mg/l CC other categories the same, the code would be

12211.

The categories and their elements are derived from the u.s. EPA (1984) gropndwater classi

fication modified byJ"ungame1JllUs of the Hawai'i groundwater environment. Am~lication of a

detailed vulnerability assessment, such as a modified fonn of DRASTIC, could be used in the

Vulnerability to Contamination category.

Brief explanations of the Status Code categories and their elements are as follows.

DEVELOPMENT STAGE. Aquifers are differentiated according to those already being used

(Currently Used), those with potential utility (Potential Use), and those having no potential

developability.

10

UTILITY. Identifies aquifers by use. Groundwater classed as Drinking may also be

Ecologically Important, but that classed as Ecologically Important may not be used for

drinking. Drinking takes precedence over Ecologically Important.

SALINITY. The gradation of groundwater from fresh to seawater is a feature of all basal

aquifers in Hawai'i. Basal aquifers comprise, by far, the most voluminous sources of ground

water. CWoride content is the class definer rather than total dissolved solids (IDS) because it is

routinely reported in the Hawai'i literature. The class limits inevitably are somewhat arbitrary

but incorporate the following logic.

1. Fresh «250 mg/l): The upper limit of the standard for drinking water is 250 mg/l

CC

2. Low (250-1000 mg/l): Much agriculture, in particular sugarcane, can be irrigated

with water containing up to 1000 mg/l CC

3. Moderate (1000 -5000 mg/l): Brackish water of this salinity may serve as feed water

for desalinization in the future.

4. High (5000-15,000 mg/l): The high salinity class, not yet seawater, is arbitrarily

designated for water that is between potentially economically valuable water and sea

water.

5. Seawater (>15,000 mg/l): True seawater has a chloride content of 18,980 mg/l.

UNIQUENESS. The classes Irreplaceable and Replaceable are direct EPA derivatives. The

island of Q'ahu does not have any groundwater of value which could be classified as replace

able.

VULNERABILITY TO CONTAMINATION. In Q'ahu because of the limits of the resources,

interconnection among groundwater sources and the relatively rapid time of groundwater

travel, aquifers can be described simply as being either vulnerable or not vulnerable to con

tamination. Most unconfined aquifers are vulnerable; confined aquifers mayor may not be. A

refinement in the degree of vulnerability may be instituted by employing some modified form

of the DRASTIC, or similar, index. The one used in this classification (High, Moderate, Low,

None) is based on familiarity with environmental conditions.

In-summary,a-gr0uI1dw-at~r-classificatiQn~scheme-whichjncludes-souIce_aLweILas_status

information has been created. The Aquifer Code consists of locators, hydrology and geology,

and reads as follows: Island-Aquifer Sector-Aquifer System-Aquifer Type. The code consists

of eight digits: one for the Island, two each for Sector and System, and three for Type

(hydrology and geology).

The Status Code contains five digits and, combined with the Aquifer Code, results in a

13-digit code. For example, the code 30104111 (11111) defines an aquifer in Q'ahu, Honolulu

Sector, Moanalua System, in which the groundwater is unconfined basal in flank lavas. The

11

last five digits tell that the aquifer is currently used to supply drinking water having less than

250 mg/l CL and that it is an irreplaceable source highly vulnerable to pollution.

Although the original scope of the project referred specifically to Class I (Special)

Groundwater, all other groundwaters in O'ahu have been classified. As a matter of interest,

Class I Groundwater Status Codes are either 11111 (Drinking) or 12n11 (Ecologically Impor

tant), in which n is a number (1-5) defining the salinity range «250 to >15,000 mg/l CO.

AQUIFER CLASSIFICATION MAPS

Accompanying this explanation of Aquifer Codes and Status Codes are fifteen quadrangles for

O'ahu (reduced from a scale of 1:24,000) on which are plotted Sector, System, and Type

boundaries. Within each Aquifer Type the Aquifer Code is printed, to which is appended the

Status Code within parentheses.

In coastal plains where sedimentary caprock aquifers rest on primary basalt aquifers, two

Aquifer and Status Codes separated by a slash are printed. The numerator code is for the upper

aquifer and the denominator for the lower aquifer.

REFERENCES

First West Engineers, Inc. 1978. Underground injection control study. Report prepared withJ.F. Mink (special Consulting Hydrologist-Geologist) for Department of Health, State ofHawaii, Honolulu (July). 71 p.

Lau, L.S., and Mink, J.F. 1987. Organic contamination of groundwater: A learning experience. J. Am. Water Works Assoc. 79(8):37-42.

Mink, J.F., and Sumida, S.T. 1984. Aquifer classification, state of Hawai'i. Tech. Memo.Rep. No. 75, Water Resources Research Center, University of Hawaii at Manoa,Honolulu. 34 p.

U.S. Environmental Protection Agency. 1984. Ground-water protection strategy.Qffi~~_QL

-- ----- --Ground.;W-atecProte-crion; Washihgtori~ D:C. 20460 {Aiig-ust).- 56 p.--+ unpaginatedAttachments I-VI.

210 I 0-222'

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LAYOUT OF AQUIFER SECfORS

AND SYSTEMS FOR O'AHU

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13

AQUIFER CLASSIFICATION EXPLANATION

AQUIFER AND STATUS CODES· AQUIFER TYPE: Hydrologyt

IS. AQUIFER SECIUR AQUIFER SYSlEM

·Where sedimentary caprock aquifers rest on primarybasalt aquifers, two Aquifer anaStatus Codes separate<lby a slas11 indicate numerator code is upper aquifer anddenominator is lower aquifer.

(11111) = Status Codewhere 1 = currently used

1 = drinking1 = fresh, <250 mg/l cr1 = irrepla:eable1 = high vulnerability

to contamination

Aquifer Code = Island+ Aquifer Sector+ Aquifer System+ Aquifer Type

Thus,30104111 = AquiferCodewhere 3 = Oahu

01 = Honolulu04 = Moanalua

1 = basal1 = unconfined1 = flank

Rev. Feb. 1990

Fresh water in contact withseawater

Fresh water not in contactwith seawater

Geologyt

Where water table is uppersurface of saturated aquifer

Aquifer bounded by impermeableor poorly permeable formations,and top of saturated aquifer isbelow groundwater surface

Where actual condition isuncertain

Horizontally extensive lavasAquifers in dike compartmentsIndistinguishableAquifer on an impermeable layerIndistinguishableNonvolcanic lithology

1 Basal

2 Confined

2 High Level

3 Confined orUnconfined

1 Unconfined

AQUIFER TYPE:

1 Flank2 Dike3 Flank/Dike4 Perched5 Dike/Perched6 Sedimentary

tIst two digits from hydrologic descriptors (pts. 1, 2).tLast digit from geologic descriptor.

Development Stage1 Currently used2 Potential use3 No potential use

Utility1 Drinking2 Ecologically important3 Neither

STATUS CODE (GROUNDWATER)

Salinity (mg/l Cn1 Fresh (<250)2 Low (250-1000)

- 3 Mooemti~I000-5000)

4 High (5000-15,000)5 Seawater (>15,000)

Uniqueness1 Irreploceable2 Replaceable

Vulnerability to Contamination1 High2 Moderate3 Low4 None

01 Palolo02 Nuuanu03 Kalihi04 Moanalua05 Waialae

01 Waimalu02 Waiawa03 Waipahu04 Ewa05 Kunia

01 Nanakuli02 Lualualei03 Waianae04 Makaha05 Keaau

01 Mokuleia02 W~Wl _03 -Kawailoa

01 Wahiawa02 Koolau

01 Koolauloa02 Kahana03 Koolaupoko04 Waimanalo

01 Honolulu

03 Waianae

02 Pearl Harbor

05 Central

04 North

06 Wmdward

3

14

UNITED STATESDEPARTMENT OF THE INTERIOR

~ OEOLOOICAL SURVEY

f.r>N

KABNA QUAORANO~

HIlWAl1-HONOLULUco. .1 JtaLA1'fD OF OAHU' r

U "'.''''UTI! SEIlIU ~1tAPH1C)I'"::.:nr

Fc

WATERRESOURCES RESEARCH CENTERUniversity of Hawaii at Manoa

KAENA,OAHU-1

1987Rev. 1990

Base Map: USGS (1:24,000 series, rev. 1983).

- SectorAquifer SystemAquifer Type

30104111 Aquifer Code(11111) Status Code

oIo

i2

2 MilesI3 Kilometers

Figure 1.1. Aquifer classification map, Ka'ena, O'ahu, Hawai'j

15

\ \-

.\ \

..

~N~.~-,-.--..='--------------:-:-'--=-,..,--------;-----,----,7'-:r-=----r-----;....,.,--~--'---,---'-:-:-:'-'156'.16'30" 158"14'00" 158°11'30" 158"09'00"

UNITED STATUD€P.t.R1'1iOO Of' THE INTERIOR

~ O~1CA1.'URVEY

.N-

WATER RESOURCES RESEARCH CENTER. University of Hawaii at Manoa

WAIANAE, OAHU-~2-

1987Rev. 1990

2 MilesI---~-""""'--.-, --"T,....'

2 3 Kilometers

7,O.,OAHU - sector~~ Aquifer System

() Aquifer Type 030104111 Aquifer Code I(11111) Status Code 0

BaSe Map: USGS (1:24,000 series, rev. 1983~

Figure 1.2. Aquifer classification map, Wai'anae, O'ahu, Hawai'i

16

UNTTED STATU+ DEPAJn1lIEHT OF THE IHTERIOR

~ OEOLOOICAL SURVO

~- -N-

..~ QUAI)ItANQU

""~c:o.....Of'QIlNU.,..~--~., 1"·OI;~...

-/,

+

"

_.~CIl

,/

Base Map; USGS (1:24,000 series, rev. 1983~

WATER RESOURCES RESEARCH CENTERUniversity of Hawaii at Manoa

2 Milesi3 Kilometers

I2

i1

oIo

WAIMEA, OAHU-9-3

1987Rev. 1990- SectorAquifer System

Aquifer Type30104111 Aquifer Code

(11111) Status Code

7,O.,OAHU. ~~

\)

Figure 1.3. Aquifer classification map, Waimea, O'ahu, Hawai'i

UNITD ""T'Ia~-~,gr. '=..JW"'OIl

'N ...

17

Base Map; USGS (1:24,000 series, rev. 1983~

- sectorAquifer SystemAquifer Type


HALEIWA,.OAHU----- - - _. -·04-

1987Rev. 1990

o 2 Milest-I----,r""'"-......,.---'T,.....'o 2 3 Kilometers

WATER RESOURCES RESEARCH CENTER.University of Hawaii at Manoa .

Figure 1.4. Aquifer classification map, Hale'iwa, O'ahu, Hawai'i

18

UNITED STATESDEPAR'T'MEHT OF' l'HE tMTERI01t

O£OLOQICAL SURVEY-.

_~_M..!JXUSGs (1:24,000 series, rev. 1983). SCHOFIELD BARRACKS, OAHU-&5

7,O..OAHU - sector1987

~D Aquifer SystemRev. 1990

\) Aquifer Type 0 2 Miles30104111 Aquifer Code I I I I(11111) Status Code 0 2 3 Kilometers


Figure 1.5. Aquifer classification map, Schofield Barracks, O'ahu, Hawai'i

19

_____---....../0


o 2 Miles1-1----,.---......".----"....,

o 2 3 Kilometers



Base Map: USGS (1:24,000 series, rev. 1983). EWA, OAHU-()

1987Rev. 1990

Figure 1.6. Aquifer classification map, 'Ewa, O'ahu, Hawai'j

20

UNITED STATESDEPAR'TMEHT OF THE INTERIOR

QEOLOOICAL SURVEY'-

P AC J J;>

JC

0

C'

4- .," . ~

+

KAHUKU OUADRAl'OLE

MMt'~:'::::U co. 1U MINUTE aula (TOPOQJlAPltIC)1I"~...t'

+ -

Base Map: USGS (1:24,000 series, rfN. 1983~ KAHUKU OAHU__O:Z _

- sector1987---- Aquifer System Rev. 1990

Aquifer Type 0 2 Miles30104111, Aquifer Code I I I I

(11111) Status Code 0 2 3 Kilometers

WATER RESOURCES RESEARCH CENTER,University of Hawaii at Manoa.'

Figure 1.7. Aquifer classification map, Kahuku, O'ahu, Hawai'j

UNITED &TATESDEPARTMENT OF THE IHTERJOl\

OEOLOOICAL SURVEY-..

21

HAUUU. OUADRANOLEHA".t.l~ULUCQ

I8l.U1DOFO*lU T

1.5 MINIITE S!R1U{tOPOORAP~~~,;,;.U''IO'



7,O..OAHU

~~

V- Sector

Aquifer SystemAquifer Type


oIo

I2

HAUULA, OAHU-(}

1987Rev. 1990

2 MilesI3 Kilometers

Figure 1.8. Aquifer classification map, Hau'ula, O'ahu, Hawai'j

22

UNITED STATESOBPARTMENT OF THE INTERIOR

OEOLOOICAl. SURVEY


30201118/30201121(1221.1)/(12212)

WAIPAHU, OAHU~_Q-l:l

7,O..OAHU - Sector1987

";;'~ Aquifer SystemRev. 1990

\) Aquifer Type 0 2 Miles30104111 Aquifer Code I , I

,(11111) Status Code 0 2 3 Kilometers

WATER RESOURCES RESEARCH CENTER. University of Hawaii at Manoa

Figure 1.9. Aquifer classification map. Waipahu, O'ahu, Hawai'i

23

'p A c F c o C E A . N


PEARL HARBOR, OAHU... . -- 0-10

1987Rev. 1990

2 Miles


-30104111(11111)

SectorAquifer SystemAquifer TypeAquifer CodeStatus Code

oIo

i2

I3 Kilometers

Figure 1.10. Aquifer classification map, Pearl Harbor, O'ahu, Hawai'i



24

UNITED STATESDEPARTMENT OF THE INTERIOR

OEOLOOICAL SURVEY,-<

7,O..OAHU

c;;'s:>

{)- Sector

Aquifer SystemAquifer Type


oIo

i2

157"46'30"

KAHANA,OAHU0-11

1987Rev. 1990

2 Miles.. '3 Kilometers

Figure 1.11. Aquifer classification map, Kahana, O'ahu, Hawai'i

UNITED STATESDEPARTMENT Of' THE INTERIOR

OEOLOOICAL SURVEY



30104111 Aquifer Code(111111 Status Code

25

c

N

KANEOHE, OAHU. 0-12

1987Re.... 199O

o 2 Miles1-1----r-......."""T,----.,.....'o 2 3 Kilometers

WATER RESOURCES RESEARCH CENTERUniversity of Hawaii at Manoa:

Figure 1.12. Aquifer classification map. Kcine'ohe, O'ahu. Hawaj'j

26

p

UN'TTED STATES. DEPARTMENT OF THE IIfTERl~

OEOLOOICAL SURVEY

~~.N'------~--_____.'"""".._____-~-=-___,__r_____'.,-__r_--___r_--__"+_---""--~---"-_:'____,-=--=---r__--_,_r__-=---__.L",--_=..,..J157"54'00" 157"51'30" 157"49'00" 157"46'30"

WATE,R RESOURCESRESEARCH CENTERUniversity of Hawaii at Manoa

HONOLULU, OAHU. . 0-13

1987Rev. 1990

2 Miles

Base Map: USGS(1:24,000 series, rev. 1983).


30104111 AquiferCode(11111) Status Code

oIo

I2

I·3 Kilometers

Figure 1.13. Aquifer classification map, Honolulu, O'ahu, Hawai'j

UMITED STATESDEPARnlIKNT OF THE INTERIOR

~ OBOLOO1CAl. a=.v~ -N

•/~--" ---I

" I

Base Map; USGS (1:24,000 series, rev. 1983).



27

MOKAJ!'UQUADItAHQLI:HA"~ULU~

taUHDOl'o.uru .

f.lI_I1l'E ......~.~...

o

MOKAPU, OAHU0-14

1987Rev. 1990

o 2 Miles1-1---r-.....L."""Tj----..r-I'o 2 3 Kilometers

WATER RESOURCES RESEARCH CENTER. . University of Hawaii at Manoa

Figure 1.14. Aquifer classification map, Mokapu, O'ahu, Haw.ai'i

28

UNITED 8TATEfSDEPAR'TlIEf'fT OF" THE INTERIOR

~ . QIOLOQlCAL SURVEY

!:lN

.'.'.'•

WATER RESOURCES RESEARCH CENTER, University of Hawaii at Manoa

KOKO HEAD, OAHU0-15

1987Rev. 1990

. ,2 Milesi3 Kilometers

i2

oIo

- sectorAquifer SystemAquifer Type

30104111 AquiferCode(11111) Status Code

Base Map: USGS (1:24.000 series, rev. 1983~

Figure 1.15. Aquifer classification map, Koko Head, O'ahu, Hawai1

Documents

REPORT DOCUMENTATION FORM WATER RESOURCES …WATER RESOURCES RESEARCH CEmER UniversityofHawaii atManoa 1 SERIfS NUMBER Technical ReportNo. 179 2 COWRR FlELD-GROUP 02-F;07-C 3 1TILE